What is ISO 14644 and why is it necessary?

ISO 14644 is an internationally recognized series of standards for the classification, design, operation, and verification of cleanrooms and related controlled environments based on airborne particle concentration. The aim is to keep airborne suspended particles (aerosols) within specific limits, preventing them from compromising product quality and process reliability in manufacturing or research processes.

In sensitive industries such as pharmaceuticals, medical devices, and semiconductors, even a microscopic particle can lead to product defects, contamination, or process failures. ISO 14644 establishes a common language across different facilities and countries by linking this contamination risk to measurable and repeatable criteria.

This page is intended to provide information to Turkish producers and exporters; it summarizes the conceptual framework of the standard and does not constitute a facility-specific declaration of conformity or measurement result.

  • It links the concentration of airborne particles to measurable classes.
  • It provides a common quality language across facilities and countries.
  • It makes product and process risks caused by contamination manageable.

Cleanroom Classifications: ISO Class 1 to 9

The ISO 14644-1 standard classifies air cleanliness into nine classes: ISO Class 1 represents the cleanest environment, while ISO Class 9 represents the environment with the highest permissible particle concentration. The number of permissible particles per cubic meter decreases exponentially as the class number decreases.

The classification logic is based on the maximum number of particles that can be found in one cubic meter of air at specific particle size thresholds (between 0.1 µm and 5 µm). The standard considers only the particle sizes that are meaningful for each class; small particles (e.g., 0.1-0.3 µm) are prioritized in very clean classes, while larger particles are prioritized in less clean classes.

The numerical equivalents of the limit values are defined by the standard and must be interpreted according to the measurement conditions at each facility. A precise class assignment can only be made through standard-compliant measurements by an accredited laboratory and a technical assessment by a qualified engineer.

  • ISO Class 1: the cleanest environment (lowest particle count)
  • ISO Class 5: a commonly used reference level for precision assembly and sterile processes.
  • ISO Class 7-8: typical target for many controlled production areas.
  • ISO Class 9: controlled but relatively highly particle tolerant environment.

ISO 14644 Standard Family

ISO 14644 is not a single document, but a series of complementary sections. Each section addresses a different phase of the cleanroom lifecycle; classification, continuous monitoring, testing methods, design, and equipment conformity are the main pillars of this series.

When used together, these components form a holistic framework demonstrating that a cleanroom is under control both during initial commissioning and throughout routine operation.

  • ISO 14644-1: Air cleanliness classification according to particle concentration.
  • ISO 14644-2: Monitoring — monitoring plan for maintaining continuous control.
  • ISO 14644-3: Test methods — standard measurement procedures for verifying performance.
  • ISO 14644-4: Design, construction and commissioning guidelines.
  • ISO 14644-14: Assessment of equipment conformity based on particle emissions.

What tests are performed in clean rooms?

Demonstrating that a cleanroom meets its intended class is possible not through a single measurement, but through a series of complementary tests. These tests are based on the methods defined in ISO 14644-3 and evaluate the facility's ventilation performance, filtration integrity, and contaminant removal capacity as a whole.

The scope and frequency of tests vary depending on the target class of the room, its intended use, and relevant industry requirements. Calibration and suitability of the measuring equipment for the method are crucial for the reliability of the results.

  • Airborne particle count (the basic measurement for classification)
  • Air flow rate and air velocity measurement.
  • HEPA/ULPA filter leak (integrity) test — DOP/PAO aerosol method
  • Measurement of pressure difference between rooms (positive/negative pressure level)
  • Recovery test — the time it takes to clean up the pollution.
  • Hourly Air Change Rate (ACH) Verification

Occupation Statuses: As-Built, At-Rest, and Operational

ISO 14644 defines that a cleanroom can be evaluated under three different occupancy conditions. The same room may exhibit different particle loads in each of these conditions; therefore, the class declaration is meaningful only if it specifies under which condition it is made.

‘The 'as-built' stage refers to the phase where the facility is complete but the equipment is installed and personnel are not present; the 'at-rest' stage refers to the phase where ventilation and equipment are working but personnel are not present; and the 'operational' stage refers to the actual production conditions where personnel are carrying out their routine activities. The most challenging and realistic assessment is usually obtained in the operational stage.

  • As-built: no equipment or personnel.
  • At-rest: systems are operational, staff are absent.
  • Operational: normal production, personnel working.

Which sectors require ISO 14644?

Cleanroom testing is critical for all industries where airborne particulate or microbial load directly impacts product safety. In many of these industries, periodic verification of cleanroom performance is a legal or customer requirement.

For Turkish manufacturers exporting, meeting the cleanroom expectations of target markets (especially the EU) can be a prerequisite for market access and supply chain acceptance.

  • Pharmaceutical and sterile product manufacturing (facilities operating under GMP standards)
  • Manufacturing of medical devices and implants.
  • Food packaging and hygienic filling lines
  • Electronic and semiconductor manufacturing.
  • Optical, precision mechanical and aerospace components.

Relationship with GMP Annex 1

Cleanroom requirements in the pharmaceutical industry are shaped by the EU GMP (Good Manufacturing Practices) Annex 1 certificate. Annex 1 defines cleanliness grades, designated A, B, C, and D, for sterile product manufacturing and closely links these grades to ISO 14644-1 classes in terms of particle limits.

For example, the most critical sterile processing areas (Grade A) require a very high level of cleanliness, while surrounding areas are supported by progressively lower grades. ISO 14644 provides the technical basis for particle measurement and classification within this relationship; Annex 1 introduces additional microbiological and operational expectations in the pharmaceutical context.

Interpreting these two frameworks together requires expertise, and a facility-specific assessment should be handled within the scope of a qualified engineer's technical evaluation.

  • Annex 1 grades (AD) are matched to ISO grades in terms of particle limits.
  • Grade A: the most critical sterile procedure area.
  • Annex 1 introduces additional microbiological and operational requirements to ISO 14644.

Information Note and Scope of AES

AES is a Type A inspection body accredited by TÜRKAK only under the scope of “6.1 Electrical Installations”. ISO 14644 cleanroom classification is outside the scope of AES's accreditation, and this page is prepared solely for general awareness purposes.

AES is NOT an accredited inspection/certification body in this context; it does not issue ISO 14644 cleanroom classification certificates.

This content is for informational purposes only and is based on a technical assessment by an authorized engineer. A binding assessment of your facility's cleanroom requirements requires an application to an accredited organization within the relevant scope.

  • AES accreditation scope: only 6.1 Electrical Installations
  • ISO 14644 classification certificate/certification is not issued by AES.
  • This content is for informational purposes only and does not constitute binding evaluation.

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Frequently Asked Questions

How many cleanroom classes are there in ISO 14644-1?

ISO 14644-1 classifies air cleanliness into nine classes, from ISO Class 1 to ISO Class 9. Class 1 represents the cleanest environment, while Class 9 allows the highest particle concentration.

What particle sizes are measured in cleanroom classification?

The standard considers threshold particle sizes between 0.1 µm and 5 µm for classification purposes. Only sizes that are meaningful for each ISO class are evaluated; small particles are decisive in very clean classes, and large particles in less clean classes.

What is the difference between as-built, at-rest, and operational states?

The "as-built" status refers to a completed facility without equipment or personnel; the "at-rest" status refers to a stage where systems are operational but personnel are absent; and the "operational" status refers to actual production conditions where personnel are carrying out routine activities. The classification statement gains meaning by specifying the status under which it is made.

What tests are performed in a clean room?

The main tests include airborne particle counting, airflow and velocity measurement, HEPA/ULPA filter leak test (DOP/PAO), inter-room pressure difference, recovery test, and air changes per hour (ACH) verification.

What is the relationship between ISO 14644 and GMP Annex 1?

GMP Annex 1 defines AD cleanliness grades for sterile production and relates them to ISO 14644-1 classes in terms of particle limits. While ISO 14644 provides the technical basis for particle measurement, Annex 1 introduces additional microbiological and operational requirements in a pharmaceutical context.

Does AES issue cleanroom classification certificates?

No. AES is only accredited under section 6.1 Electrical Installations; it does not issue ISO 14644 cleanroom classification certificates. The content on this page is for informational purposes only and is subject to technical evaluation by an authorized engineer.